PROJECT SUMMARY Metastasis is the main cause of death from solid tumors including colorectal cancer (CRC). My long-term goal is to develop more selective therapeutic options to prevent or reduce the incidence of CRC metastasis by understanding how changes in de novo fatty acid synthesis contribute to metastatic disease. Fatty acid synthase (FASN), a key enzyme of de novo lipid synthesis, is significantly upregulated and activated in CRC, and its activity is associated with poor prognosis, higher risk of disease recurrence, and death. I have identified FASN as a potential target for advanced stages of disease and showed that upregulation of this enzyme is a key mechanism supporting metastasis in CRC. However, the underlying mechanisms of regulation of metastasis by FASN are still poorly understood. This NCI Transition Career Development Award (K22) application proposes a comprehensive research and training plan to study the role of FASN in regulation of cancer cells survival and metastasis in CRC. Two novel mechanisms of regulation of survival and metastasis by FASN in CRC will be elucidated in this proposal. First, preliminary studies show that overexpression of FASN is associated with an increase in cellular respiration, including ?-oxidation, inhibition of autophagy, and accumulation of lipid droplets. Therefore, Aim 1 will elucidate the role of FASN in reprogramming of metabolic pathways and lipid storage in order to maintain energy homeostasis and promote survival of cancer cells. Furthermore, our preliminary studies suggest that the primary product of de novo fatty acid synthesis, palmitate, is selectively used for sphingolipid synthesis and overexpression of FASN increases the level of sphingosine-1-phosphate (S1P), a bioactive sphingolipid, known to stimulate migration and invasion of cancer cells. Therefore, in Aim 2, I will test the hypothesis that FASN promotes metastasis via activation of sphingosine kinases and an increase in S1P signaling. I will utilize biological samples from patients, human primary cells and PDX models, which are the most advanced models for pre-clinical target and drug evaluations. These models will be used in conjunction with state-of-the-art approaches, including Stable Isotope-Resolved Metabolomics (SIRM) to evaluate the effect of FASN overexpression on cancer metabolism. The differential expression of FASN in normal versus cancer cells makes de novo lipogenesis a desirable target for therapeutic intervention. I anticipate that the proposed work will significantly advance our understanding of the role of FASN in advanced CRC and potentially lead to the development of novel therapeutic strategies to treat this disease.